AN ABSTRACT OF THE THESIS OF
DAVID DOUGLAS COUGHENOWER for the
(Name)
in
OCEANOGRAPHY
MASTER OF SCIENCE
(Degree)
presented on
(Date)
(Major)
J 97
Title: EARLY SPRING NUTRIENT CONDITIONS IN SOUTHEASTERN
ALASKAT S INSIDE1 PASSAGE
Abstract approved:
Redacted for Privacy
Observations were made of salinity, temperature, nitrate +
nitrite, phosphate, silicate, total available nitrogen, and chlorophyll
a in nine areas of the Alaskan Inside Passage during April of 1971.
In general all properties indicated the water to be well mixed through-
out this area. The conservative properties were particularly uniform.
The greatest range in temperature from the surface to ZOOm was only
1.10 C.
The largest salinity range over the same depth was 2.0
0/00
Spring phytoplankton blooms were just beginning to appear.
Clarence Strait, in the southern part, presented the most evidence of
biological activity. Values of chlorophyll a in this area were the
highest observed (7. 25 mg chl a/rn3) outside of Auke Bay. This area
also had the most density structure, probably due to stabilization
brought on by warming. N : Si : P ratios for Clarence Strait indicate
that silicate could become limiting in this area.
The only other area, outside of Auke Bay, that had evidence
(high chlorophyll a) of biological activity was Taku Inlet. The N Si : P
ratios for this area indicate that nitrate will probably be the limiting
nutrient.
Low oxygen values (Z ml/l) from the bottom of several deep
basins indicate the possibility of anaerobic conditions developing as
the water column stabilizes.
Flow within the Inside Passage seems to be controlled by freshwater and saltwater inputs. Several major sources of both types of
water are found. Tides and winds contribute to the circulation of the
area but the mixing of saltwater and freshwater seems to be the predominant force.
Local effects such as land runoff, glacial melt, input from hot
springs and bottom topography are important in determining water
conditions.
Total available nitrogen may be a better indicator of photosyn-
thesis than nitrate. TAN : P ratios tend to remain higher during
photosynthesis than nitrate : P ratios.
Early Spring Nutrient Conditions of Southeastern
Alaska's Inside Passage
by
David Douglas Coughenower
A THESIS
submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Master of Science
June 1972
APPROVED:
Redacted for Privacy
Professor of Oceanography
in charge of major
1
Redacted for Privacy
Chairmanof Oceanograph
Redacted for Privacy
Dean of Graduate School
Date thesis is presented &g/7(f1V i'91..
Typed by Susie Kozlik for David Douglas Coughenower
To Linda, who was more help than anyone
ACKNOWLEDqEMENTS
I would like to express my deepest appreciation to Professor
Herbert Curl Jr. First of all for giving me the opportunity to under-.
take this thesis and secondly for his help and guidance in its prepara-
tion. A good major professor is half of the battle and I have one of
the best.
I owe a very special debt of gratitude to Louis I. Gordon. His
suggestions and consultation concerning the TAN analytical method
were invaluable. Just as important has been his friendship and the
example of research excellence that he follows.
The data acquisition system was made possible through the work
of Chuck Samuelson and Peter Becker. Without this system and their
help during the cruise much of the data for this thesis would not have
been possible. A sincere thanks to Debbie Kirk and Cheryl Alber
for their help during the cruise. Cheryl is also to be thanked for
analysis of the chlorophyll samples after the cruise, Since the cruise
Debbie has contributed many helpful suggestions and much support
during the data reduction.
It is impossible to detail all of the support my colleagues have
given while this thesis was being prepared. However, the following
people have contributed in one way or another: Elliot Atlas, Saul
Alvarez-Borrego, John Callaway, Mark Halsey and Rich Tomlinson.
I would like to acknowledge the following grants and contracts
for the support they provided: Sea Grant Project 061, NOAA 2- 35187;
U. S. Department of Interior, Water Quality Trainee Program contract
o. 5T1WP-111-05; ONR contract no. N00014-67-A-0369-007; ad
NSF grant 6A-12113.
TABLE OF CONTENTS
Page
INTRODUCTION
1
METHODS AND MATERIALS
3
3
3
Cruise Tracks
Sampling Methods
Nutrient Methods
RESULTS I
Sections
Fredrick Sound to Taku Inlet
Chatham Strait
Clarence Strait
Glacier Bay
Icy Strait
Lynn Canal
West Stephens Passage
Gastineau Channel
Sumner Strait
RESULTS II
Pr op e r ties
Temperature
Salinity
Sigma -t
Oxygen
Nutrients
Total Available Nitrogen
Chlorophyll a
DISCUSSION
Hydrography and Circulation
Circulatio,n Control
Major Areas
Features of Specific Areas
Gastineau Channel
Glacier Bay
Distribution of Nutrient Properties
Nitrate
Preformed Nutrients
5
6
6
6
8
10
12
12
14
17
17
17
22
22
22
24
24
24
25
26
26
28
28
28
30
30
30
31
32
32
33
Page
Biologically Related Features
TAN vs. Nitrate
Phytoplankton Bloom Areas
Potential Fertility
36
39
39
40
SUMMARY
41
BIBLIOGRAPHY
43
APPENDIX
46
LIST OF FIGURES
Page
Figure
1
2
3
4
Southeastern Alaska's Inside Passage
Contours of nutrient, hydrographic and chlorophyll
a data for Transect A-A', Fredrick Sound to Taku
Inlet
7
Contours of nutrient, hydrographic and chlorophyll
a data for transect G-G', Chatham Strait
9
Contours of nutrient, hydrographic and chlorophyll
a data for transect I-I', Clarence Strait
5
7
8
9
10
11
12
13
11
Contours of nutrient, hydrographic and chlorophyll
a data for transect F-F', Glacier Bay
6
4
13
Contours of nutrient, hydrographic and chlorophyll
a data for transect F-F', Icy Strait
15
Contours of nutrient, hydrographic, and chlorophyll
a data for transect D-D', Lynn Canal
16
Contours of nutrient, hydrographic and chlorophyll
a data for transect C-C', West Stephens Passage
18
Contours of nutrient, hydrographic, and chlorophyll
a data for transect B-B', Gastineau Channel
19
Contours of nutrient, hydrographic and chlorophyll
a data for transect H-H', Sumner Strait
20
Dominant patterns of flow in the Inside Passage
due to saltwater and freshwater inputs
29
Comparison of deep nitrate + nitrite values from
inside the Passage with open ocean water
34
Contour of nitrate + nitrite data illustrating the
northerly increase
35
LIST OF APPENDIX FIGURES
Figure
1
2
3
Physical layout of continuous UV system
49
Interfacing of UV system with automated
nitrate analysis
50
Linearity test for (NH4)2SO4 and glycine
55
LIST OF TABLES
Page
Table
1
2
3
Maximum and minimum salinity and temperature
values at surface for each transect
23
Dissolved oxygen data from several deep basins
25
Nitrogen, TAN, Silicon and Phosphorus ratios for
surface and deep water at selected stations throughout the Inside Passage
37
LIST OF APPENDIX TABLES
Page
Table
1
Recovery of (NH4)25O4 and amino acid standards
52
2
Percent recovery at 80 mm. residence time
53
3
Percent recovery of glycine
56
EARLY SPRING NUTRIENT CONDITIONS OF
SOUTHEASTERN ALASKA'S INSIDE PASSAGE
INTRODUCTION
As a fishing ground and natural water way, the Inside Passage
is an extremely important part of Alaska (Figure
1).
For example,
in 1968 this area recorded 70 million kilograms of fish and shellfish
caught compared to 204 million kilograms for the entire state (State
of Alaska, 1968). For the oceanographer this area presents some
rather unique hydrographic features and conditions found nowhere else
in North America. The combination of these factors would seem to be
sufficient reason for extensive studies of th%s area. However, the
literature contains very little published data on the Inside Passage.
The most significant work in this area is a survey of its physical
characteristics by Pickard (1967). A few individual features have
been well studied. Phytoplankton ecology by Bruce (1969), Iverson
(1971), and Schell (1971), and physical features by McLai,n (1968) and
Powers (1963) but a comprehensive look at its nutrients would seem
desirable.
The investigation described in this paper is presented only as a
beginning, to what is hoped will become a more complete description
of nutrient distribution and cycling in the Inside Passage. The data
presented here was gathered during a single cruise from 10 to 21
2
April, 1971, through selected portions of the Inside Passage. Data
obtained in Auke Bay during the cruise and the summer of 1971 are
discussed by Kirk (1972). Additional observations at different times
of the year for several years will be needed to complete the nutrient
picture.
The cruise sampling plan was designed with biological features
in mind. Consequently the samples are concentrated in the upper 50m
with only a few deeper samples at each station.
The nutrients surveyed are silicate, phosphate, nitrate + nitrite,
and total available nitrogen (TAN). Temperature, salinity and sigma-t
data are presented along with the nutrients. A few oxygen values are
reported for some of the deeper areas of the Passage. Chlorophyll a
data are presented as an indicator of primary production.
Total available nitrogen refers to the total of all forms of nitrogen in seawater that can be utilized as a nutrient source by phytoplankton.
This includes nitrate, nitrite, ammonia and most amine
containing compounds (1. e. dissolved amino acids and Urea). TAN is
a biologically meaningful measurement since phytoplankton can use all
of these sources equally well, although they do show a thermodynamically directed preference (Harvey 1940).
3
METHODS AND MATERIALS
Cruise Tracks
Nine areas of the Inside Passage were surveyed during this
cruise.
The cruise tracks and station numbers are given in Figure 1.
Throughout this paper the different tracks are referred to at times by
letter designation and at times by their common name.
The stations
are numbered sequentially from the beginning of the cruise to the end.
Sampling Methods
Salinity, temperature and depth data were acquired using a
Bisset-Berman Model 6040 STDS sensor. The STD system includes a
pump that provides a water sample from the same depth as the sensor
(Becker and Curl, 1971). Nutrient samples were collected in 60 ml
plastic bottles. At some stations duplicate samples were taken, one
set being analyzed at sea for nitrate + nitrite and total available nitrogen (TAN), the other set frozen. For all stations at least one set of
samples was frozen and returned to Corvallis for phosphate, silicate,
nitrate and TAN analysis.
The maximum pumping depth was ZOOm. At a few stations (6, 49,
59, 61, 63) bottle casts were made to obtain salinity, temperature,
nutrient and oxygen samples from greater than ZOOm.
;
\9v
':\Auke
580 N
I
(
.Tomas
-'-'I
::.:
iaConte
'skut
70H
40Km
131°W
141
:
Figure 1. Southeastern Alaska's Inside Passage.
5
Nutrient Methods
All the silicate, phosphate, and most of the nitrate and TAN
analyses were done in the Corvallis laboratory using a three-channel
Technicon® AutoAnalyzer® system. The silicate method is basically
that of Armstrong, Stearns and Strickland (1967) as modified by Hager,
Gordon and Park (1968).
The phosphate analysis is that of Bernhart
and Wilhelms (1967) with several modifications by Atlas etal. (1971).
The nitrate + nitrite is that of Wood, Armstrong, and Richards (1967)
with modifications for automated analysis by Hager etal. (1968). TAN
was determined using the photo-oxidation method of Armstrong,
Strickland and Williams (1966) as modified for automated analysis by
Coughenower (See Appendix I).
The reagents for the Winkler oxygen determinations were those
of Carpenter (1965). Salinity samples from the bottle casts were
analyzed in Corvallis using a Bisset-Berman Model 630 inductive
salinometer.
In most cases two liters of water were filtered to obtain chiorophyll a samples.
These samples were analyzed using the spectro-
photometric method of Richards and Thompson (1952).
RESULTS I
Sectio ris
The nine areas surveyed are designated by transect lines on the
chart of the Inside Passage (Figure 1). The hydrographic and nutrient
data, for each of these transects,are contoured in Figures 2 - 10. The
contour intervals used in these figures are temperature, 0.5°C;
salinity, 0.2 o/oo; sigma-t, 0. 1 units; phosphate, 0. 2 1j.M; silicate,
5 p.M; nitrate + nitrite, 5 riM; TAN, 5 p.M; chlorophyll a, 1 mg chi
a/rn3. The dashed line at 200m that appears on some of the figures
is used to indicate a depth scale change.
Fredrick Sound to Taku Inlet
Transect A-A' (Figure 2) takes in the area Fredrick Sound to
Taku Inlet. It has a mean depth of about ZOOm, and is strongly influ-
enced at its northern end by the Taku River (average mean flow, 260
m3/sec). The southern end comes under the influence of Fredrick
Sound and in between are a variety of inputs from streams, rivers and
glaciers (Pickard, 1967). The slight decrease in temperature around
station 5 is an example of the input of colder water from Tracy and
Endicott arms which are glacier fed. Stations 5, 6 and 7 all show the
slight temperature inversions discussed later.
The most prom-
inent feature in this area is the cold, low nutrient area between stations
7
-4:$1;
FIID( SOI
20
'
I.'
20
I
\
O-t
TAJU) ILET
JL
32,2O
FIEDRIII( SOlIdO
m
TAXU INLET
I
Ssty
ADRtIOIIND
TAKIJ INLET
,,/
\
0_V
'_,
L'1567
Figure 2. Contours of nutrient, hydrographic and chlorophyll a data
for transect A-A', Fredrick Sound to Taku Inlet.
2-4. This is probably due to cold water coming from LeConte glacier
and Thomas Bay, then flowing North. This water tends to stay to the
East side of Fredrick Sound.
Chatham Strait
Transect G-G' (Figure 3) is the area known as Chatham strait.
It also runs North-South with an average depth of 600m. Station 67
is representative of open ocean water and its influence in the strait
can be seen on all parameters. The reduced sigma-t value around
station 66 is probably due to input from a stream, Deer Creek, directly
opposite this station.
The influence of colder, less saline (plus higher nutrients)
water from Glacier Bay and Lynn Cannal on the northern end of
Chatham Strait is evident in the sigma-t, temperature and nutrient
contours. This is an interesting effect with a wedge of colder Less
saline water
poking
its way into warmer, saltier ocean water. This
effect's similar to, but not the same as the classic estuary system.
The unusual temperature structure occurring around station 64
and moving south seems to be related to fresh water input of the
Baranof River (13 m3/sec., Pickard, 1967), located near this station.
This river is fed partly by a hot spring, whose volume and temperature
are 0.3 m3/sec. and 16-50°C (Waring, 1965).
61 P
61
62
66
64
676
)(
IC
2C
mNui
CHATHAM STRAIT
Nit,.t./Ntt,it.
CHATHAM STRAIT
aM
61
/
62
3
64
65
3o
20
CHATHAM STRAIT
CHATHAM STRAIT
Tatal N
Salinity
.61
62
63
frt
65
6
7
CHAIHAM STRAIT
CHATHAM STRAIT
Tup.rat.q.
Pttatp.t.
aM
62
63
64
66
St
------
/ 45
2(
20
CHATHAM STRAIT
ChI.r.phyll a
mi nhIF&
\
-..-----.--40
CHATHAM STRAIT
Silinat.
aM
Figure 3. Contours of nutrient, hydrographic and chlorophyll a data
for transect G-GT. Chatham Strait.
10
About 12 hours elapsed between station 64 and 65 due to a storm
that blew north up Chatham Strait with 40+ knot winds. Because of
this the joining of the contour lines in this area may not be justified.
The slight decrease in temperature at the surface of station 65
is probably due to water coming out of Fredrick Sound.
I }ave just pointed out several places in Chatham Strait where
local influences have quite an effect on water conditions.
The Inside
Passage is a very dynamic area with high tidal ranges and frequent
winds.
The importance of local effects cannot be overlooked.
Clarence Strait
Clarence Strait (Figure 4) is another of the larger areas surveyed. Also running North-South, it has an average depth of 400m.
This area is open to the ocean at its southern end and again we see
the estuary effect, that was observed in Chatham Strait, evident here
in the temperature and nitrate contours.
The sigma-t contours have more stratification than any other
area surveyed. This is probably due to stabilization brought on by
warming. The temperatures here are about two degrees warmer
than any other area. This warming may result from this area being
further south, but I think the primary effect is from the input of
warmer ocean water.
11
:T;; c7
40
RAIT
80
72
7,3
-c
2
I
i;l
il I
3120
31.40
31.80
-J
07
6
--32.80
20
-
72
7,3
-T2
5'
Ia.ArErdcE sTRArr
-
AITRAT
l-Ni
t.atiIers
I
-..- I
73
7
7'
30 -__ -
l.0
35
01
20
20
40
a
SiIi..t
aM
60
Figure 4. Contours of nutrient, hydrographic and chlorophyll a dat.a
for transect I-F, Clarence Strait.
12
A result of this warming and stabilization is the appearance of
biological activity at stations 72 and 73. This is evident on both the
nutrient and chlorophyll a contours. This was the most biologically
active area, outside of Auke Bay.
Glacier Bay
With an outer sill depth of about 60m the bay is restricted in its
mixing with adjacent areas. As its name implies, Glacier Bay was
formed by a complex of glaciers, presently receding; consequently its
bottom profile is very irregular. It has a mean mid-inlet depth of
370m (Pickard, 1967). The bay is basicly glacier fed and the tempera-
tures observed here were cold and uniform. Salinity and sigma-t
(Figure 5) indicate that the cold glacial melt remains near the surface
while the deep water is well mixed.
Icy Strait
Transect E-E', known as Icy Strait, has a mean depth of 240m
and is open to the ocean at its western end.
The sill depth is 66m so
that any exchange between Icy Strait and the ocean takes place near
the surface. Depending on the winds and tide Icy Strait acts as a channel for water coming out of Glacier Bay, down Lynn Canal or in from
the ocean.
These combined waters then flow into the northern end of
13
54
55
54
56
9
250
24.8...
1(
57
56
55
58 K
s__._
150
25
S
1T
II
10
20
GLACIER BAY
\ .
\../
Nit,.t./8iUitS
55
3180
56
57
\3l'\ '-3f.2o
31.00
S
10
1>
20
/
GtACIER BAY
T.tN
5
/<
K*\
K
GLAER BAY
.oqIo--
57
/)
K
5ML
/
/
I
K
'tTV
2
Figure 3. Contours of nutrient, hydrographic and chiorophylla data
for transect F-F, Glacier Bay.
14
Chatham Strait. The high nutrients and low chlorophyll a (Figure 6)
mark this region as one of low productivity.
At the time this area was surveyed there was a layer of lower
salinity water, probably from Glacier Bay, lying at the surface and
some colder, saltier water moving west near lOOm.
Lynn Canal
Transect D-D' is only the southern end of Lynn Canal. The
portion surveyed has a mean depth of 500m.
Icy Strait and then Chatham Strait.
Lynn Canal merges with
The presence of water from Lynn
Canal is apparent in Chatham Strait (Figure 7).
It is conceivable that water conditions at the northern end of
D-D are influenced by water coming out of West Stephens Passage
(C-C'). A comparison of stations 46 and 47 for all properties (Figures
7 and 8) would seem to support this idea. However, no data is avail-
able for the area North of station 47.
No salinity, temperature or sigma-t data are available for station
48 and joining the contour lines between stations 47 and 49 may be
questionable. There are reduced nutrient concentrations down to
lOOm at station 48 but the chlorophyll a data are not above average.
The absence of temperature and salinity data makes this feature diff icult to explain.
15
I
I
ICY STRAIT
Sip..-t
--
EN-Ni
ICY STRAIT
Nit,sls/Nitsits
(
ICY STRAIT
ICY STRAIT
Tet.l N
S.11,,ity
50
52
St
1.9
2.7
2.7
ICY STRAIT
T.mp.r.t.rI
50
----------------- o.t --------- 1T::-j
--
/
ICY STRAIT
CEIIrspE9II
IY STRAIT
Sill,. I.
.eEli&
Figure 6. Contours of nutrient, hydrogra-phic and chlorophyll a data
for transect E-Et, Icy Strait.
16
LYNN CANAL
0
Siio.-t
LYNN CANAL
NiU.*./Niflit.
SM
51M,
SU M,
45
31.90 ___________
IC
30
)
32.10
0
LYNN CANAL
O
S.Iisi*y
T,l.IN
.0
SUM,
9101
2.1 --------------
0
LYNN CANAL
.0
0
SUM,
LYNN CANAL
SM
5 _ U U,
Figure 7. Contours of nutrient, hydrographic and chiorophylla
for transect D-DT, Lynn Canal.
-1ata
17
West Stephens Passage
Transect C-C' (Figure 8) is actually the northern end of Stephens
Passage. This area has a mean depth of about 90m. A small area
of topographically upwelled water is located around stations 44 and 46.
This is evident in salinity, temperature, and sigma-t contours, and
less evident in the nutrient contours. Station 45 and perhaps Auke
Bay is the source of some low nutrient water below lOm.
Gastineau Channel
Gastineau Channel (Figure 9) is a short, shallow stretch of water
that branches NW off of Stephens Passage. It has a mean depth of
less than 40m and drops off at its mouth to over 200m. Gastineau
channel is closed at its northern end by mud flats during most of a
tidal cycle. Juneau harbor, is located near its northern end (station
12), is probably one of the prime nutrient sources for this area.
Sumner Strait
Sumner Strait, transect H-H' (Figure 10), has a mean depth of
240m and a maximum depth of 450m. Sumner is open to the ocean at its
western end and the effect of ocean water can be seen in the increasing
salinity and temperature at station 68. The saltier and slightly warmer
ocean water moves into the strait below 50m and the fresher water
18
_25J
-
4S
46
4
r'
42_
C
44
5
51
10
F5
WEST STEPHENS PASSAGE
Nitrate/Nitrite
WEST STEPHENS PASSAGE
Sigma-t
aM
SN-Mi
F
C.
to
IC
WEST STEPHENS PASSAGE
WEST STEPHENS PASSAGE
Total N
Salinity
uM
SN-Mi
SNMi
F
F
44
46
44
42
4
46
45
C
F,
-
5
to
10
WEST STEPHENS PASSAGE
WEST STEPHENS PASSAGE
Temperature
SN-Mi
F
F
4
II
5N-Mi
O(
/
____10___
46
44
Phosphate
uM
46
44
42
4
,-."-1
F
45
___55-___-11
,,
SI
SI
70
10
WEST STEPHENS PASSAGE
WEST STEPHENS PASSAGE
Silicate
Chlorophyll a
mgchl/mJ
SN-Mi
Figure
SNMi
uM
F
F
.
Contours of nutrient, hydrographic and chlorophyll a data
for transect C-C, West Stephens Passage.
C
19
GASTINEAU CHANNEL
Sigma-t
5NMi
GASTIN [AU CHANNEL
Total N
uM
5NMi
GASTINEAU CHANNEL
GASTINEAU CHANNEL
Temperature
Phosphate
.c
5NMi
eM
5NMi
I.o
GASTINEAU CHANNEL
I
I
Silicate
uM
5NMI
Figure 9. Contours of nutrient, hydrographic and chlorophyll a data
for transect B-B', Gastineau Channel.
20
_.!-
.- 0_
20.0
STRAIT
I
/\
Is -.31.50
'C
STRAIT
/\
su.
I
I
\RSTRAn
16
0
/\
J30 25y
:::::::::::::::::::::
ii
STRMT
I
\ SlRsVR STRAIT
STRAIT
L
/\
/ \
Figure 10. Contours of nutrient, hydrographic and chlorophyll
data for transect H-H', Sumner Strait.
21
moves out above 50m.
salinity of only 0. 3
This area is well mixed with an increase in
0/00
down to 200m.
The nutrient contours follow a pattern similar to that of salinity
and temperature. Nutrient concentrations are higher below SOm.
The deeper concentrations are similar to those found at station 67.
Chlorophyll a data from Sumner Strait reveals only average
amounts of biological activity.
22
RESULTS II
Properties
Generally what we observed during the cruise were initial
oceanographic conditions as the spring bloom was beginning.
The
Inside Passage system was well mixed hydrographically, and the ver-
tical differences observed in all parameters were small, except in
Auke Bay (Kirk, 1972).
Temperature
The winter conditions that still existed throughout most of the
Inside Passage were reflected in the water temperatures. The maximum surface temperature (Table 1) was 5. 1°C at station 74, while the
rni.nimum was 2. 1°C at station 46.
The greatest range in tempera-
ture, from the surface to ZOOm, was only 1. 1°C at station 67.
Slight temperature inversions were observed in parts of Stephens
Passage, Glacier Bay, Sumner Strait and Clarence Strait. Cold glacial runoff flowing over slightly warmer bottom water is the most
likely explanation of these inversions. However, in the case of
Clarence Strait it is also due to the influence of open ocean water.
Table 1. Maximum and minimum salinity and temperature values at surface for each transect. Also
maximum range, surface to ZOOm. The enclosed number is the station where value was
obs erved.
TEMPERATURE 00
SALINITY o/oo
Max
Mm
A-A'
B-B'
31.86(5)
C-C'
31.81(46)
D-D'
31.85(47)
30.13(8)
30.90(12)
31.40(42)
31.79(49)
E-E'
31. 83(51)
31. 79(50)
F-F'
31. 81(54)
30. 59(59)
G-G'
32.25(67)
31.73(68)
31.27(71)
31.83(61)
31.47(69)
31.17(72)
H-H'
I-I'
31. 11(10)
Range
Max
1.71(8)
4.6(7)
3.5(11)
2.6(42)
2.5(47)
3.0(52)
3.0(54)
4.4(67)
3.7(68)
5.1(74)
----0.30(49)
0.57(51)
0.79(59)
0.38(66)
0.33(69)
1.97(73)
Mm
2.4(2)
2.4(12)
2.1(46)
2.4(47)
2.8(50)
2.2(59)
3.2(61)
3.6(69)
4.0(71)
Range
+1.6(6)*
-0.4(49)
-0. 3(52)
+0. 4(55)
-1.1(67)
+0.2(68)
+0.6(72)
range indicates increasing temperature with depth.
qJJ
24
Salinity
Surface salinity values confirm that this was a time of minimum
run off (Pickard, 1967) for most of the rivers. A minimum surface
salinity (Table 1) of 30. 13
0/00
was recorded at station 8, near the
mouth of the Taku river. The maximum surface salinity, 32. 25
0/00,
was observed at station 67.
Sigma-t
Sigma-t values at the surface (Table 1) reached a maximum of
25.6 at station 65 and a minimum of 23.9 at station 8. The greatest
range of sigma-t, between the surface and 200m, was 1.6 units at
station 73. The minimum range over the same depth was 0. 1 units at
stations 63 and 68. Under the conditions of temperature (2-5°C) and
salinity (30-32 o/oo) observed in the Inside Passage sigma-t values
are most strongly influenced by changes in salinity.
Oxyg en
Only a few oxygen samples were taken, by bottle cast, from
several deep, isolated basins (Table 2). The depth of these basins
ranged from 325m to 785m and the oxygen values at these depths averaged 2. 3 ml/L. The surface values at these same stations were 7. 1
7. 7 mi/L. The age of the water and the ventilation rate are unknown
-
25
but these areas could conceivably become anoxic (if water column
stability continued or increased).
Table 2. Dissolved oxygen data from several deep basins.
Station
Depth (m)
02 (mi/L)
50
200
325
7.7
6.6
4.0
2.3
49
690
2.1
59
112
200
287
6.9
7.1
7.0
63
200
300
600
785
7.1
5.0
2.5
6
0
2.4
Nutrients
For the non-conservative nutrients it would not be meaningful to
report maximum and minimum surface values or ranges. They often
passed through several maximums in the upper lOOm. The contour
maps (Figures 2 - 10) give a much better picture of nutrient distributions. Some general trends in the nutrients will be mentioned here.
Slightly higher nutrient concentrations were observed in the eastern
most transect (A-A') compared to another major transect, G-G'. This
could be due to A-A' receiving a more thorough mixing because it is
26
shallower.
Also conditions in G-G' are partly determined by open
ocean water.
Total Available Nitrogen
Throughout the areas surveyed the difference between TAN and
nitrate + nitrite ranged from 2-13k M with the average closer to 4
M.
By definition this difference includes ammonia, urea arid dissolved
amino acids. The 13 M difference was observed at the surface of
station 8. Chlorophyll data from this station does confirm some bio-
logical activity in the upper lOm. However, the TAN, nitrate difference at stations 72 and 73 (also biologically active) was not significantly
greater than average. Possibly this indicates that the bloom in the
latter area was just getting started, with fewer dissolved organic
compounds in the water.
Chlorophyll a
Chlorophyll a data is presented as an indicator of primary biological activity. Samples were taken to 50m but in most cases this
will encompass the photic zone and be an accurate indicator of primary
production. The maximum surface value for chlorophyll a was 7. 25
mg chl a/rn3 (station 72) while the minimum was 0.23 rng chl a/rn3
(stations 51, 52). The maximum in Auke Bay was 15 rng chl a/rn3
27
(Kirk, 1972). During the summer of 1971 chiorophylla averaged
25
mg/rn3 (Zakar, 1972). The overall average was very close to 1 mg
chi a/rn3. This is evidence that the productivity of the Inside Passage
was not very great at the time of this cruise and that the spring bloom
was just beginning.
DISCUSSION
The word that best describes the Alaskan Inside Passage is
dynamic. High tidal ranges, frequent winds, heavy land runoff and
high precipitation characterize some of the events that influence water
conditions in this area. A rugged topography carved by receding gla-
ciers makes its presence felt on the physical character of the land.
Even during the time of this cruise, a time when water conditions were
mostly uniform, there were enough differences to make things intere sting.
Hydrography and Circulation
Circulation Control
Surface salinity data from this cruise and salinity information
from Pickard (1967) were used to plot the influx of saltwater and the
out flow of freshwater in the Inside Passage (Figure 11). This diagram
is not intended to be a quantitative representation of transport. Its
purpose is to present an easily read, semi-quantitative picture of the
predominant fresh and saltwater sources and the most probable route
these inputs take through the Inside Passage. The large solid arrows
indicate major saltwater sources and the smaller solid arrows the
minor saltwater sources.
The major freshwater sources are mdi-
cated by the hollow.arrows and the minor sources by the thin arrows.
Figure 11. Dominant patterns of flow in the Inside Passage due to
saltwater and freshwater inputs. The large, solid arrows
represent major sources of high salinity water; the small,
solid arrows are minor sources of saltwater. Major
freshwater inputs are marked by the hollow arrows and
minor sources by the thin arrows.
.:::.\
i\
I
'.:\\.
i-./+\
L
;
.:::
Auko
Bay
-
\
-1
\'
I
'I
r
rJ
\
Ir
#
thomas
,
1/
-
Bay
k
134°W
cft'ç;k
1
K
30
As an input weakens, away from the source, major sources become
minor sources.
The intrusion of saltwater up Chatham Strait is surprisingly
strong. Freshwater coming out of Taku Inlet seems to split going into
Stephens Passage and its influence is seen as far west as Lynn Canal.
According to Pickard (1967), most of the freshwater coming out of the
Stikine-Iskut rivers flows south.
These surface flows are subject to
the influence of winds, tidal currents, and increased runoff but the
pattern shown is probably the predominant one.
Major Areas
Fredrick Sound to Taku Inlet, Chatham Strait and Clarence Strait
are the three areas that seem to dominate the Inside Passage, both in
size and in their influence on water conditions.
The first of these is
one of the main channels for freshwater into the system and the other
two are main sources of saltwater. The other areas surveyed are
smaller, with interesting and in some cases unique features that con-
tribute to the three major areas.
Features of Specific Areas
Gastineau Channel
The sigma-t and salinity contours are well structured in the
upper 40m (Figure 9) with a layer of fresher water at the surface,
31
probably the result of runoff. During a tidal cycle an exchange of water
between Gastirieau Channel and Taku Inlet can be expected. This ex-
change seems to take place below lOm. The chlorophyll data around
station 10 and [Fare slightly higher than average at the surface. The
lower nutrient and higher chlorophyll a values near the bottom of the
channel may be the result of primary production.
Circulation patterns for the summr in Gastineau Channel have
been described in a study done by the FWPCA
(1966)
in August of
1965.
They suggest that the observed freshwater layer at the surface probably
comes from Stephens Passage because there are so few local sources
in Gas tineau Channel. The exchange of water between Gas tineau
Channel and Stephens Passage is described as slow with input at the
surface and output below [Om. For winter conditions they predict a
reversal of this trend with a slight output at the surface and input at
depth. The data in Figure
9
tends to support their prediction of an
input below lOm during winter conditions.
Glacier Bay
Pickard
(1967)
noted some distinctive conditions in the inlets
with icebergs. He found low temperature and high salinity at the head
of the inlet. A small range of sigma-t indicated less stability and
more vertical mixing. He reported high 02 at depth due to vertical
mixingand low biological activity in the upper layers leading to low
32
oxygen demand from detrital material. Many of these same conditions
were observed by us in Glacier Bay with the exception of higher
salinities at the head. However, we noted very little ice during this
cruise.
In general nutrients are somewhat lower in Glacier Bay (Figure
5) than in other parts of the Inside Passage. I think it is to be expected
that glacial waters would be a poorer source of nutrients than land
runoff. Muir Inlet is slightly higher in nutrients than that coming out
of Tarr Inlet. The chlorophyll a data for stations 55-59 are slightly
higher than average. A decrease in nutrients for these same stations
may indicate a small amount of biological activity.
Once the water leaves Glacier Bay it can move in two directions
depending on the tide and winds. An outgoing tide would take it west
toward the ocean and an incoming tide would take it east into Icy and
Chatham Straits. An incoming tide can also influence water conditions near the mouth of Glacier Bay, bringing water from Icy Strait
into the bay. Station 54 was taken on an incoming tide.
Distribution of Nutrient Properties
Nitrate
A comparison was made between deep nitrate + nitrite values
within the Inside Passage and deep values from the stations nearest
33
the open ocean (Figure 12). There seems to be very little deep ex-
change of nitrate between station 60 and the inner stations. This is
understandable because of the sill depth (60m).
Nitrate exchange between station 67 and stations within the
Straits (66 and 68) seems to take place around lOOm. Station 74 is not
as typical of open ocean water as 67 because of its location. The only
nitrate influence of station 74 on station 73 seems to be at 50m.
The stations as they are plotted in Figure 12 are oriented essentially North to South. The higher numbered stations being further
south. Discounting a good deal of noise in going from station to station
there seems to be, at all three depths, a tendency toward higher
nitrate + nitrite values as one moves further north. If station 60 is
omitted as not being a part of the Inside Passage the trend is even
stronger. The northerly increase in nitrate is also evident in Figure
13, a contour of nitrate data. The strongest increase is noted north
of station 65.
Nitrate + Nitrite and salinity values for all stations and all depth
were regressed against each other to see if they might be correlated
in some way. The resulting correlation coefficient (0. 24) indicates
that there is no statistical relationship between the two properties.
Preformed Nutrients
Calculation of preformed N and P in deep water (greater than
STATIONS
30
25
0
20
15
10
Figure 12. Comparison of deep nitrate + nitrite values from inside the Passage with open ocean
water.
STATIONS
2
7
50I
"0
4% \
-15
E
=
100
'U
4ss
1'3
= Pycnocline
2
C'
Figure 13. Contour of nitrate + nitrite data illustrating the northerly increase.
u-I
36
300m) averaged 11.8 pj.M for N and 1.06 p.M for P. The largest con-
centration of preformed N and P was found at 200m at several places
in the Inside Passage (Table 3). Below 200m the preformed nutrients
decreased rapidly until at 600m the preformed N and P were 10.8 and
0.91 p.M respectively, or about 30% of the total N and P.
In several places the preformed nutrient concentrations above
ZOOm were much greater than the oxidized nutrients. One possible
explanation for this is that during the winter months preformed nutri'-
ents are supplied to the surface waters by land runoff. If the Inside
Passage were mixed down to 200m this would account for the high
preformed nutrients above ZOOm.
Below ZOOm oxidized nutrient con-
centrations become much greater than preformed. This could be due
to organic matter raining out of the upper layer and decomposing below
ZOOm. Low oxygen values below 200m tend to support this idea. Addi
tional data will be necessary to clear up this point.
Biologically Related Features
The N
:
P ratios for some of the deeper stations, as deter-
mined from nitrate + nitrite and phosphate have an average of 14 :
1
(Table 3). This is slightly less than the widely accepted value of 16 :
1
(Redfield, Ketchum and Richards, 1963), but quite similar to the 11.9
to 13. 9 : 1 found in the San Juan channel by Phifer and Tornpson (1937).
37
Table 3. Nitrogen, TAN, Silicon and Phosphorus ratios for surface
and deep water at selected stations throughout the Inside
Passage. Also preformed N and P for those stations where
data was available.
Sta.
Depth(m)
N
TAN
6
0
14
14
15
13
200
325
:
Si
:
P
1
13
26
26
27
14
1
1
8
0
12
20
32
1
46
0
15
17
28
1
56
0
13
12
14
14
18
1
24
1
15
14
25
23
1
200
12
13
---
27
28
1
----
26
1
25
27
1
200
59
61
63
0
0
14
540
15
0
14
14
160
600
72
73
15
1
1
1
0
11
1
14
16
17
22
200
25
1
0
6
8
10
15
17
21
1
200
1
N.M
Pp.M
17.2
11.4
1.46
1.26
18.3
1.55
23.2
1.82
13.1
101
21.9
10.8
1.64
0.91
It seems reasonable that Redfieldts ratios would not hold com-
pletely in areas where local conditions such as the proximity of land,
the inflow of rivers, and local flora and fauna may change the picture.
It is interesting to note however, that if the N : P calculations are
made using TAN and phosphate an average of 15 : 1 is obtained.
In areas showing son
biological activity (station 72 and 73) the
N : P ratios from nitrate and phosphate decrease, indicating that
nitrate could become limiting. However, the ratios obtained from
TAN and phosphate remain quite high (Table 3).
Silicate is not a universal requirement of living matter, however,
it is present in large quantities in the tests of diatoms, which dominate
the phytoplankton in cooler waters. Richards (1958) found a linear
relationship in the changes in the concentration of silicate and phosphate in the Western Atlantic. He obtained an Si : P ratio of 15 :
1
or about the same as nitrogen. The two biologically active areas ob-
served during this cruise had quite different Si : P ratios. At station
8 the ratio was 32 : 1 (Table 3) at the surface. This high ratio could
reflect a large concentration of silicate being dumped into the area by
the Taku river. This area had the highest silicate values observed.
Station 73, the other biologically active area, had Si : P ratios of
17:1 at the surface. This approaches Richards value and indicates
that silicate could reach a limiting concentration.
From the Si : TAN : P ratios discussed above it would appear
that at station 8 nitrogen will eventually become the limiting nutrient.
At station 73, however, silicate will probably be limiting.
39
TAN vs. Nitrate
The measurement of TAN rather than nitrate seems to have
distinct advantages in regard to the photosynthetic potential of an area.
When measuring initial conditions TAN values give a more accurate
N : P ratio and a better estimate of the nitrogen pool. This permits
accessment of the limiting nutrient, if any, and the potential fertility
of an area. Measurement of TAN during a bloom gives a more accurate picture of the nitrogen available to the phytoplankton. N : P
ratios using nitrate may decrease during a bloom while ratios calculated from TAN may remain quite high (Table 3).
PhvtoDlankton Bloom Areas
Two areas outside of Auke Bay gave evidence that spring phyto-
plankton blooms were in progress. Those two area, Taku Inlet and
Clarence Strait, seem to suggest that blooms were initiated by stabilization of the water column, in accordance with the critical depth concept of Sverdrup (1953). In the case of Clarence Strait stabilization
brought on by warming produced the mixed depth necessary to initiate
the bloom. In Taku Inlet density differences due to freshwater input
could have established the mixed depth and triggered the bloom.
Potential Fertility
Harvey (1947) suggested that the potential fertility of natural
waters may be determined from the total phosphorus or total combined
nitrogen.
40
The potential fertility was defined by Redfield, Ketchum and
Richards (1963) as the quantity of organic matter which could be produced by photosynthesis from a unit volume of seawater if it was
brought from depth to the surface and illuminated there until the limiting nutrients were exhausted.
Station 46 was selected to make a calculation of the potential
fertility of the Inside Passage. This station is of a reasonable depth
that might allow all the nutrients to reach the photic zone. Nitrate
was assumed to be limiting and by using Redfieldts ratios an average
parcel of water was found to be capable of producing 2. 18 g C/rn3.
This compares favorably with the theoretical value of 2. 74 g C/rn3
calculated by Redfieldetal. (1963). Carrying the calculation one step
further we can determine that the potential fertility of the entire water
column is 386 g C/m2. Ryther (1960) has estimated that the phyto-
plankton of the oceans as a whole contain 3 g C/rn2. The estimate of
potential fertility serves only to indicate the maximum production that
could occur in the photic zone during the year.
This estimate is made assuming no recycling of the available
nutrients. If recycling were considered this estimate might be in-
creased several fold. Other factors that tend to decrease this theoreti-
cal estimate are losses due to grazing, respiration and sinking from the
water column. The actual production for this area can be expected to
be much less than this theoretical estimate.
41
SUMMARY
1.
During the time of this cruise the Inside Passage was well
mixed to at least ZOOm. Spring phytoplankton blooms were just beginning in a few areas.
2.
Of the nine areas surveyed three stand out as being most
important in setting the nutrient conditions in the Inside Passage. The
three areas are Fredrick Sound to Taku Inlet, Chatham Strait and
Clarence Strait. Perhaps because of their size these three areas tend
to dominate the circulation in the Inside Passage. The other areas
are smaller with particular features that contribute to the three major
areas.
3.
The importance of localized effects in determining water
conditions in the Inside Passage should not be overlooked. Some of
the local effects found to be important are: land runoff, glacial melt,
input from hot springs, bottom topography, tides and winds.
4.
The most important of the local influences seems to be input
of open ocean water. The input of saltwater up Chatham Strait is
surprisingly strong. The circulation of the Inside Passage seems to
be controlled by the input of fresh and saltwater.
5.
Some of the deep isolated basins in the Inside Passage may
become anoxic if the water column stability increases with the onset
of warmer weather.
42
6.
Phytoplarikton blooms in the Inside Passage are probably
initiated by stabilization brought on by warming.
The southern areas
are most likely to warm up first and therefore should be the first areas
to have blooms.
7.
Nitrate is probably the limiting nutrient in most areas of the
Inside Passage. The N : P ratios were very similar to Redfield's
values (16
1) and the ratio decreased in the few areas that had bio-
logical activity.
TAN may be a better predictor of photosynthesis than
nitrate. TAN : P ratios tend to remain high during photosynthesis.
8.
Slightly higher nutrient concentrations were observed in the
eastern most transect (A-At) compared to the western most transect
(G-G'). There was also a slight tendency for nitrate + nitrite con-
centrations to increase as one moved north.
9.
Glacier Bay exhibited many of the same conditions that
Pickard (1967) observed in his 'iceberg" inlets (i.e. low temperatures,
small sigma-t range and high
2
at depth).
The data presented here are only the beginning to what, it is
hoped, will be a more comprehensive look at nutrient properties in
the Inside Passage. Additional cruises to these same areas, at other
times of the year, will be necessary to enlarge the nutrient picture.
Two cruises for 1972 are already in the planning stages.
43
BIBLIOGRAPHY
Armstrong, F. A. J. C. B. Stearns and J. D. 1-1. Strickland.
1967.
,
The measurement of upwelling and subsequent biological processes by means of the Technicon® AutoAnalyzer® and associated equipment. Deep Sea Research. 14(3):381-389.
Armstrong, F. A. J. and Susan Tibbitts. 1968. Photochemical
combustion of organic matter in seawater, for nitrogen, phosphorous and carbon determination. J. Mar. Biol. Assoc. U. K.
48:143-152.
Atlas, Elliot L., S. W. Hager, L. I. Gordon and P. K. Park.
1971.
A practical manual for use of the Technicon® AutoAnalyzer® in
seawater nutrient analysis; Revised. Oregon State University,
Department of Oceanography, Reference 71-22. 55 p.
Becker, Peter and Herbert Curl, Jr. 1971. Oceanographic environmental data acquisition system at Oregon State University.
Interface, The Bissett-Berman Corporation. 1(2):1 -2.
Bernhardt, H. and A. Wilhelms. 1967. The continuous determination
of low level iron, soluble phosphate and total phosphate with the
AutoAnalyzer®
Technicon Symposium, 1967. Vol. I. p. 386.
.
Bruce, H. F. 1969. The role of dissolved amino acids as a nitrogen
source for marine phytoplankton in an estuarine environment in
Southeastern Alaska. Doctoral dissertation. Corvallis, Oregon
State University. 124 numb. leaves.
Carpenter, Jams.
1965. The Chesapeake Bay Institute technique
for the Winkler dissolved oxygen method. Limnology and
Oceanography. 1O(1):141-143.
FWPCA, U. S. Department of Interior, Northwest Region. 1966.
Oceanographic and related water quality studies in Southeastern
Alaska, August 1965. Portland, Oregon. 64 p.
Hager, S. W., L. I. Gordon and P. K. Park. 1968. A practical
manual for use of the Technicon® AutoAnalyzer® in seawater
nutrient analysis. Final Report to Bureau of Commercial
Fisheries, Contract 14-17-0001-1759. Oregon State University,
Department of Oceanography, Ref. No. 68-33. 31 p.
Harvey, H. W. 1940. Nitrogen and phosphorus required for the
growth of phytoplankton.
J. Mar. Biol. Ass U.K. 24:115-123.
44
Harvey, H. W. 1947. Fertility of the ocean. Proc. Linnean Soc.
London. 158:82-85. (Cited in: The Sea, Vol. 2, ed. by M. N.
Hill. New York. Interscience Pub1ishers.
Iverson, R. L. 1971. A systems approach to pelagic ecosystem
dynamics in an estuarine environment. Doctoral dissertation.
Corvallis, Oregon State University. 111 p.
Kirk, D. 1972. Physical hydrography and nutrient nitrogen budget
of Auke Bay, Alaska. Master's Thesis in progress. Corvallis,
Oregon State University.
McLain, Douglas. 1968. Oceanographic Surveys of Traitors Cove,
Rivellagigedo Island, Alaska. U. S. Fish and Wildlife. Special
Scientific Report, Fisheries No. 576.
Phifer, L. D. and T. G. Thompson. 1937. Seasonal variations in
the surface waters of San Juan channel during the five year
period, January 1931 to December 30, 1935. J. Mar. Res.
1:34-53.
Pickard, G. L. 1967. Some oceanographic characteristics of the
larger inlets of Southeast Alaska. J. Fish. Reach. Bord.
Can. 24(7):1475-1506.
Powers, Charles F. 1963. Some aspects of the oceanography of
Little Port Walter estuary, Baranof Island, Alaska. U. S. Fish
and Wildlife Service. Fisheries Bulletin. 63:143-164.
Redfield, A. C., B. H. Ketchum and F. A. Richards. 1963. The
influence of organisms on the composition of seawater. The
Sea, Vol. 2 ed. by M. N. Hill. New York. Interscience
Publishers.
Richards, F. A. and T. G. Thompson. 1952. The estimation and
characterization of plankton populations by pigment analysis.
II. A spectrophotometric method for the estimation of plankton
pigments. 3. Mar. Res. 11:156-172.
Richards, F. A. 1958. Dissolved silicate and related properties of
some western North Atlantic and Caribbean waters. 3. Mar.
Res. 17:449-465.
45
Ryther, 3. H. 1960. Organic production by planktonic algae and its
environmental control. The Pymatuning Symposium in Ecology.
Pymatuning Laboratory of Field Biology, University of Pittsburg.
Special Pub. No. 2 pp. 72-83. (Cited in: The Sea, Vol. 2. ed.
by M. N. Hill. New York. Interscience Publishers.)
Schell, Donald M. 1971. Uptake and regeneration of dissolved organic
nitrogen in Southeastern Alaskan marine waters. Ph.D. Thesis,
University of Alaska, College, Alaska. 142 pp.
State of Alaska. 1968. 1968 Alaska catch and production, commercial
fisheries statistics. Department of Fish and Game (statistical
leaflet no. 17). Richard C. Nelson, Supervisor of Statistics.
Sverdrup, H. U. 1953. On conditions for the vernal blooming of
phytoplankton. 3. Conseil Explor. Mer. 18:287-295.
Waring, Gerald A. 1965. Thermal springs of the United States and
other countries of the world- -a summary. Geological Survey
Professional Paper. No. 492.
Zakar, K. 1972. Phytoplankton Ecology in Auke Bay, Alaska.
Master's Thesis in progress. Corvallis, Oregon State University.
APPENDIX
46
APPENDIX I
AN AUTOMATED TECHNIQUE FOR THE ANALYSIS OF TOTAL
AVAILABLE NITROGEN BY ULTRAVIOLET OXIDATION
tnt rod uct ion
Dissolved inorganic nitrogen compounds in seawater, such as
nitrate, are often analyzed because in most marine situations these
are the most abundant. However, with the increased interest being
shown in organic nitrogen compounds as nutrient sources for phytoplankton (Bruce,
1969;
Guillard,
1963;
Griffiths,
1965)
nitrate values
alone do not always provide the biological oceanographer with an ade-
quate picture. A more useful measurement would be total available
nitrogen (the total of all forms of nitrogen in sea water that can be
utilized as a nutrient source by phytoplankton). This should include
nitrate, nitrite, ammonia and any amine or amide containing cornpounds (e. g. dissolved amino acids) that phytoplankton can utilize.
Total available nitrogen (TAN) is a biologically meaningful measure-
ment since phytoplankton can use all of these sources equally well,
although they do show a thermodynamically directed preference
(Harvey, 1940).
One means of obtaining total available nitrogen values would be
to measure each form separately and sum them. This is within present
methodology. However, replacing four or five methods with a single
47
one would mean a great savings in equipment and time.
This is most
important if a sea-going method capable of giving real-time data is
sought.
The only method I found that seemed to satisfy the single-method
criterion for TAN was the ultraviolet oxidation technique of Armstrong,
Strickland arid Williams
(1966).
High-intensity UV radiation is used
to oxidize reduced forms of nitrogen compounds (ammonia, amino
acids, etc.) into nitrate and nitrite. The original nitrate and nitrite
content of the sample remains relatively unchanged during radiation.
The result is that the total nitrogen content of a sample is in inorganic
forms (nitrate and nitrite) that can be easily analyzed by colorimetric
techniques (Wood, Armstrong and Richards,
1967).
There is a major drawback to the original method. The radia-
tion time recommended by Armstrong etal.
(1966)
is three hours for
12 samples. This is far too slow for a method designed to provide
real-time data at sea. I have worked on this method with two objectives in mind. To reduce the radiation time as much as possible and
to automate the method for use with a Technicon® AutoAna1yzer.
METHODS AND MATERIALS
The method is basically that of Armstrong, Strickland, and
Williams (1966). The one important difference is the use of a con-
tinuous coil of small diameter (2mm i. d.) quartz tubing in place of the
discrete sample tubes (Figure Al). Use of the continuous coil makes
the nitrate + nitrite analysis readily adaptable to the Technicon®
AutoAnalyzer® (Figure AZ).
After oxidation of the ammonia (and
most amine containing compounds) to nitrate and nitrite, samples were
analyzed according to the method of Wood, Armstrong, and Richards
(1967) as adapted to the AutoAnalyzer® by Atlas etal. (1971).
The ultraviolet source is a 1200 watt lamp (189A, Hanovia Lamps)
utilizing a 550 VAC power source (supplied by Hanovia). The UV
system is cooled by a 100 cfm blower and the lamp is shielded with a
quartz tube to prevent over-cooling, as suggested by Armstrong et al.
(1966).
Sampling
is
at the rate of 0.42 cc/mm for seven minutes. The
initial standard is usually run for eight minutes and the final ASW
blank about 10 minutes (i. e. when large differences in concentrations
are expected sampling time is increased). This samplingrate permits
7-8 samples per hour with standards being run every 10 samples and
blanks every 20 samples. Prior to entering the UV system samples
are filtered through glass fiber paper and three percent hydrogen peroxide is added (0.015 cc/mm.), as an oxygen source.
49
I Source
iartz Shield
iartz Sample Coil
i1 Support
luminum Cylinder
wer Junction
lower
iput Output
8(
>
AA
Figure A. Physical layout of continuous UV system.
50
er
(
r()
)
p
Figure A2. Interfacing of UV system with automated nitrate analysis.
51
RESULTS
A wide range of AutoAnalyzer® pump tubes are available (0. 015
cc/mm. to 3. 90 cc/mm.) (i. e. a wide range of residence times).
However, the volume requirements of the nitrate + nitrite analysis
dictate some limitations on the pumping rates that can be used in the
UV system.
The volume of sample coming out of the UV system can-
not be less than the sampling tube going into the nitrate + nitrite analy-
sis. Three different pumping rates were tried in the UV system
(Table Al). The resulting residence times were 60, 80 and 110
minutes. The recovery of the different standards was about 3% better
for the 80 minute residence time than for 60 minutes. The concentra-
tions in Table Al are calculated using an F-factor determined from a
nitrate standard as suggested by Strickland and Parsons (1968).
These
calculations indicate that even at 80 minutes the oxidative process is
not ye complete. Manny, Miller and Wetzel (1971) have suggested
that in seawater samples it is the oxidation of ammonia to nitrate and
nitrite that requires the most time.
From the above results one would expect the 110 minute resi-
dence time to give an even better percent recovery. However, the
recovery for this residence time was the lowest of the three. In order
to obtain this residence time the nitrate + nitrite analysis had to be
altered to accept a smaller volume. These changes may have altered
52
Table Al. Recovery of four different standards at three different
residence times. Al6 M NO3; B=24 1jM (NH4)2SO4;
Cl0 M glycine; D8 1M NO3 + 12 M NH3. Each value
is an average of 3 samples.
% Recovery
STD.
Conc.
A
15.4*
96
B
20.6
9.3
17.9
86
C
D
94
89
110 Mm.
80 Mm.
60 Mm.
% Recovery
Conc.
% Recovery
Conc.
15.6
21.4
10.0
18.1
97
89
14.7
19.4
81
100
8.0
80
91
16.8
84
92
*Calculations were made using anonUV treated NO3 standard.
the linearity of the analysis. Also, the longer the residence time the
more difficult it becomes to maintain sample integrity.
After determining an optimum residence time several known
concentrations of different amino acids and one mixed solution were
tested in the UV system. The percent recovery of all the amino acids
and the mixture (Table AZ) was 95-100 with the exception of arginirle
(8 6%).
The structure of arginine might be expected to make it more
difficult to decompose. Armstrong, Strickland, and Williams (1966)
reported some difficulty in recovering urea. No similar difficulty was
encountered using this UV system. Eight M urea gave a 95% recovery.
There is a tendency for sample to sample boundaries to become
mixed as they pass through the UV system.
This leads to a somewhat
poorer response time when compared to samples that pass only through
the nitrate analysis. However, the system does give a linear response
53
Table AZ.
Percent recovery at 80 minutes residence time.
Concentration
N Containing
Compound
% Recovery
(NH4)2SO4
12
100
(NH4)2SO4
16.5
100
(NH4)2SO4
24
90
Glycine
12
100
E;]
95
Aspartic Acid
12
100
Proline
10
100
Arginine
8
86
Mixture
16*
95
Urea
*
4 j.M Proline + 4
.LM
Arginine + 4 iM Aspartic Acid
54
over a suitab'e concentration range. A linearity test for (NH4)2SO4
over a concentration range of 3 to 40 M was performed (Figure A3)
as was one for glycine over a range of 5-30
M.
A departure from linearity for glycine occurs at the higher concentrations (about 12% at 30 uM) (Figure A3). I am convinced that the
reason for this departure is an insufficient supply of O rather than
too short of a exposure to UV radiation.
One of the problems encountered was maintaining a good bubble pattern through the UV system. I finally concluded that it would
be impossible to keep an integral bubble pattern in a sample that was
being slowly pumped through 24. 4 meters of 2mm tibing while being
subjected to intense heating and gas generation. The best that could
be hoped for was to keep the samples separated without using an ex-
cessive volume of sample. Although the bubble pattern emerging
from the UV system was very irregular I found that a sampling time of
seven minutes was sufficient to produce a good plateau on the recorder.
The residence time is largely controlled by the pump tubes used
(both air and sample tubes must be considered). However, the small
volume of the quartz coil (60m1) makes the residence time particularly
susceptible to volume changes. For example, the expansion of the air
segments as they pass through the UV system are enough to change
the residence time considerably. Once the system reaches thermal
equilibrium the residence time will become constant but changes in
LU
0z
4.3
m
0
4
(I)
.2
28
40
CONCENTRAT(ON (jiM)
Figure A3. Linearity test for (NFI4)2SO4 and glycine.
(6
56
ambient temperature can change this equilibrium. At least a 30
minute warm up time is recommended.
The generation of gas within the UV system can also have a
drastic effect on the residence time. Because of this I found it necessary to use only a 3% H202 solution rather than the 30% used by
Armstrong,
(1966).
The freshness of the H2O solution also needs to be considered.
Over a (long) period of time a 3% solution of HOz will deteriorate.
This will change both the oxidative power of the H202 and the residence
time of the sample.
Table A3. Percent recovery of glycine.
Cone. (PM)
5
10
20
30
*
Recovered Cone.
% Recovery
5.0*
9.8
18.7
26.3
100
Calculations based on F-factor of 5 uM glycine
98
93
88
57
DISCUSSION
A small diameter sample circulating around and in close proximity to the UV source provides a continuous sample stream readily
adaptable to automated analysis. It has the added advantage of reducing the time required for oxidation of amine and amide containing
compounds. By varying the pumping rate through the quartz coil the
residence time of the sample can be controlled.
Automating the photo-oxidation technique for analyzing total
available nitrogen has increased the sampling rate considerably.
Armstrong etal. (1966) required more than three hours to analyze 12
samples. Using the automated technique described here it is possible
to analyze 24 samples plus blanks and standards in three hours. Being
a continuous system this rate is constant. Although this rate does not
approach the rates now possible for nitrate, phosphate and silicate
(Atlas etal. , 1971) it is rapid enough to be useful at sea. The system
is portable and rugged enough to be safely taken to sea. The system
described here was tested at sea during April of 1971 with very satis-
factory results (see thesis text).
The insufficient supply of 02 noted in the glycine linearity test
seems also to be the explanation of the lower recovery (90%) of 24 pM
(NH4)2SO4 (Table AZ). The glycine curve was obtained using the pres-
ent UV system where 3% H202 is added at 0.015 cc/mm. The
recovery of the 24 p.M (NH4)2SO4 was determined using the same systern. The (NH4)2SO4 linearity test (Figure A3) and the other recoveries
of amino acids (Table AZ) were obtained using a system in which one
drop of 30% H202 was added to 60 ml of sample, by hand, before
introducing it into the UV system. Apparently the diluted HO2 does
not supply sufficient O to oxidize the higher concentrations.
I would suggest trying oxygen gas in place of air as the segmenting agent in the UV system. The oxygen would replace the H202
as the oxidizing agent. This should provide a more adequate source
of
°2 atoms since H202 tends to be destroyed fairly rapidly by UV
radiation (Manny, etal., 1971).
Although automation of this technique and reduction of radiation
time have been accomplished there are several areas that I feel deserve additional research. Armstrong and Tibbets (1968) reported
little success with photos ens itizers. However, they tried only a few
while using a lower intensity lamp. The application of the right photo-
sensitizing compound could reduce the residence time further.
Anything that could be done to improve the efficiency of the systern would be useful. Perhaps using a double layer sample coil might
improve the absorption of UV radiation. Also polishing the inside of
the aluminum cylinder might increase the UV radiation reflected back
towards the sample coil.
The sampling rate presently being used (0. 42 cc/mm.) is almost
too slow for the nitrate analysis system. Using a double coil might
make it possible to increase the sample flow rate (giving a smoother
flow through the system and better sample separation) and yet decrease
the sampling time (which effectively increases the number of samples
per hour).
Since total available nitrogen is a biological parameter we must
know how well this method performs in 'real life.
All the data for the
development of this technique came from ammonia salts and prepared
amino acids. The next step is to use the automated TAN method in a
nitrogen budget experiment with an algal culture.
BIBLIOGRAPHY
Armstrong, F. A. J., and Susan Tibbitts. 1968. Photochemical
combustion of organic matter in seawater, for nitrogen, phos phorus and carbon determination. J. Mar. Biol. Assoc., U. K.
48:143-152.
Armstrong, F. A. J., P. M. Williams and J. D. H. Strickland.
1966.
Photo-oxidation of organic matter in seawater by ultraviolet
radiation, analytical and other applications. Nature. July 30,
1966. p. 481-483.
Atlas, Elliot L., S. W. Hager, L. I. Gordon and P. K. Park.
1971.
A practical manual for use of the Technicon® AutoAnalyzer®
in seawater nutrient analysis; Revised. Oregon State University.
Department of Oceanography. Reference 71-22. 55 p.
Bruce, H. F. 1969. The role of dissolved amino acids as a nitrogen
source for marine phytoplankton in an estuarine environment in
Southeastern Alaska. Doctoral dissertation. Corvallis, Oregon
State University. 124 numb, leaves.
Griffiths, D. J. 1965. The oxidative assimilation of organic substrate
by algae. Sci. Progr. 53:553-566.
Guillard, Robert R. L. 1963. Organic sources of nitrogen for marine
centric diatoms. In: Symposium on Marine Microbiology (Carl
H. Oppenheimer, editor). p. 93-103.
Harvey, H. W. 1940. Nitrogen and phosphorus required for the
growth of phytoplankton.
J. Mar. Biol. Assoc. U. K. 24:115-
123.
Manny, B. A., M. C. Miller and R. G. Wetzel. 1971. Ultraviolet
combustion of dissolved organic nitrogen compounds in lake
waters. Limnol. oceanogr. 16(1):71 -85.
Strickland, J. D. H. and T. R. Parsons. 1968. Apracticalhandbook
of seawater analysis. Bull. Fish. Res. Bd. Can. 167. 311 p.
Wood, F. D., F. A. J. Armstrong and F. A. Richard.
1967.
De-
termination of nitrate in seawater by cadmium-copper reduction
to nitrite. 3. Mar. Biol. Assoc. U. K. 47:23-31.